There has heretofore been proposed a radiation thermometer wherein an external acoustic opening, which is an opening of a living being is selected as a measurement site for, measuring a body temperature in a short period of time, and infrared rays from an eardrum and the external acoustic opening which are a measurement target are detected with an infrared ray sensor to measure a body temperature of the living being. In such a radiation thermometer, a probe is inserted into an external acoustic opening which is an opening of a living being so that an infrared ray sensor detects an infrared ray which is incident upon the probe. Since the probe does not perfectly face the eardrum even when inserted into the external acoustic opening, both the temperature of the eardrum and temperature of the external acoustic opening are measured. However, the external acoustic opening usually has approximately the same temperature as the eardrum, and therefore, it is possible to measure a temperature which is close to the eardrum temperature even though both temperatures are measured.
An example of such radiation thermometer is described in Japanese Patent Publication No. 63851/1994. This radiation thermometer measures temperature only once at the moment that a measurement switch is pressed, with a probe inserted into an external acoustic opening in advance. However, since the probe is usually left in a room or the like before measurement and hence in many cases has a lower temperature than an eardrum temperature, when the probe as such is inserted into an external acoustic opening, the external acoustic opening which is used to have approximately the same temperature as an eardrum is cooled by the probe. For this reason, the radiation thermometer which is described in the abovementioned Patent Publication measures a temperature of the cooled external acoustic opening together with an eardrum temperature, and therefore, cannot accurately measure the eardrum temperature.
Noting this, a radiation thermometer described in Japanese Laid-open Patent Publication No. 263125/1990 measures a temperature which is close to an actual eardrum temperature rather than an eardrum temperature which is cooled by the probe. This radiation thermometer includes a peak hold circuit so as to display the highest temperature of measured temperatures. As a manipulation method for this purpose, before inserting the probe into the external acoustic opening, a measurement switch is to be pressed to start measuring of a temperature. Since measurement of a temperature is executed before inserting the probe into the external acoustic opening in this manner, it is possible to measure a temperature which is close to an eardrum temperature at the time of insertion of the probe before the external acoustic opening is cooled, i.e., a peak temperature, instead of measuring the eardrum temperature and a temperature of a cooled external acoustic opening.
However, this radiation thermometer starts temperature measurement in a condition in that an external acoustic opening is cooled by the probe if a user (measuring person) fails to follow operation procedures and presses the measurement switch after inserting the probe into the external acoustic opening as described above, and therefore, the radiation thermometer fails to measure a desired peak temperature, ends up in measuring a lower eardrum temperature than the peak temperature and a temperature of the cooled external acoustic opening, and eventually displays a lower temperature than an actual body temperature.
On the other hand, since the peak hold circuit of the radiation thermometer which is described in Japanese Laid-open Patent Publication No. 263125/1990 is designed to be reset each time the measurement switch is pressed and body temperature measuring operations are started, as the measurement switch is pressed again after inserting the probe into the external acoustic opening, a maximum temperature detected during insertion is reset. The radiation thermometer accordingly displays a maximum temperature measured after the measurement switch is manipulated for the second time. The displayed temperature is an eardrum temperature and a temperature of the cooled external acoustic opening cooled by the probe, and as such, is lower than an actual body temperature.
The present invention has been made in view of the problems above. Accordingly, an object of the present invention is to provide a radiation thermometer which starts temperature measurement with a measurement switch upon manipulation thereof before inserting the probe into the external acoustic opening and displays a maximum temperature of measured temperatures as a body temperature, characterized by indication of an erroneous operation after judging whether the measurement switch is appropriately manipulated or avoids displaying a temperature which is measured by erroneous operation.